Snap action thermostat with amplified actuating movement



July 2, 196s F, REINGRUBER 3,391,370

SNAP ACTION THERMOSTAT WITH AMPLIFIED ACTUATING MOVEMENT Filed Aug. 4,1965 [UIMM 'a um.. '.111

[NVE/VTR. FPA N K RE/NGPUBER Arrowf Y United States Patent O 3,391,370SNAP ACTION THERMOSTAT WITH AMPLIFIED ACTUATING MOVEMENT I FrankReingruber, Bartlett, N.H. 03812 Filed Aug. 4, 1965, Ser. No. 477,118 1Claim. (Cl. 337-343) ABSTRACT OF THE DISCLOSURE A bimetal securedintermediate its ends on a heat transfer plate, with both ends free forthermostatic action and an inverted V-strut engaged at its opposite endswith the free ends of the bimetal imparts snap switch opening andclosing movements to a spring toggle biased form of switch blade.

The invention herein disclosed relates to thermostats for generalcontrol purposes.

Special objects of the invention have been to provide a simple practicalsnap action thermostat, with amplified movement actuating means,rendering it particularly sensitive and responsive to small as well asgreater temperature changes.

This has been accomplished by means of a spring switch blad-e biased inone direction by a spring strut operating as a toggle link to snap theswitch blade in opposite directions and by providing a bimetal anchoredat the center so as to ilex both ends and by engaging the ends of aV-shaped strut with the opposite ends of the bimetal and the center ofthe strut in position to stress the switch blade over the dead center ofthe toggle structure.

Other novel features of the invention and desirable objects accomplishedare set forth and will appear in the course of the followingspecification.

The drawing accompanying and forming part of the specificationillustrates a present commercial embodiment of the invention. Structure,however, may be modified and changed as regards the presentillustration; all within the true intent and scope of the invention ashereinafter defined and claimed.

FIG. 1 in the drawing is a broken, part vertical sectional view of thethermostat in the normal, circuit closed position.

FIG. 2 is a broken detail view illustrating the reverse, open circuitposition of the parts.

FIG. 3 is a bottom plan view with cover removed to show the toggleaction switch.

FIG. 4 is a top plan view of the switch mechanism on substantially theplane of line 4-4, FIG. 1.

FIG. 5 is a plan view of the heat transfer bottom cover and the bimetalmounted thereon.

FIG. 6 is a broken sectional detail of the control knob with yieldingterminal point.

FIG. 7 is a broken sectional detail of one of the wire terminal bindingposts.

FIG. 8 is a diagram illustrating action of the centersecured bimetal.

The bimetal is shown in the form of a ilat strip 10, anchored at thecenter by means of a rivet 11, on a cover plate 12, forming a heattransfer member and enclosing the bottom of a rectangular case 13,having extended lugs 14 at the bottom by which the unit may be securedin operative position.

The opposite ends of the bimetal are turned up to form abut-ment lugs15, 16, for the angularly related legs 17, 18 of a V-shaped strut archedat the center and carrying a correspondingly shaped insulating button19, having a transverse pressure transmitting ridge 20 in engagementwith the Switch blade to be controlled.

3,391,370 Patented July 2, 1968 rice The ends of the angular sidedexpansible and contractible strut are shown as anchored to the ends ofthe bimetal strip by having extended lugs 21 projecting throughcorresponding openings in the bimetal.

The angularly spread legs of the V-strut are shown as stiffened byembossed ribs 22 so as to serve as straight rigid pressure transmittingelements.

The switch blade consists in the present illustration of a spring strip23 secured at one end at 24 and carrying a contact 2S at the oppositeend engageable with a companion stationary switch element 26.

Movement of the contact carrying end of the switch blade is limited inthe opposite direction by a spaced insulator 27.

Snap spring toggle action of the switch blade is accomplished by meansof a spring strut or toggle for-ming link 28 connected at one end withthe free end of the switch blade and fixed at the opposite end at 29 toa stationary lug or post 30.

This spring strut is shown as an integral piece struck out of the bodyof the spring switch blade and left connected thereto at the contact endat 31 and free at the opposite end for engagement with the stationaryabutment 30.

The spring strut 28 is bent or bowed as shown in FIGS. l and 2, toenable necessary yield in passage of the switch blade over dead center.

The pressure transmitting button 19 of the strut engages a transverselycontinuous portion 32 of the switch blade, FIGS. 1 Aand 3, at a pointinward from the anchorage point 29 of the spring strut and the opening33 by which this strut is cut out of the blade is extended back of thestationary lug 30 so that the pressure center 32 on the blade Imaytravel from the position at one side of center 29, FIG. l, to theopposite side of such center, as shown in FIG. 2, thus to eect the snaptoggle movement from the FIG. 1 to the FIG. 2 position.

The spring toggle switch will remain in the latter, open position ofFIG. 2 so long as the center 32 determined by the thermostat is 'abovethe fixed toggle center 29.

As the bimetal retreats from the FIG. 2 toward the FIG. 1 position, thecenter 32 will lower below the dead center position 29, allowing thespring strut 28 to snap the switch blade back into the FIG. 1 positionwith the switch contacts 25, 26 again in engagement.

The switch mechanism as shown in FIGS. 3 and 4 is all carried by achannel form base 34, which is pivotally mounted in the case on a crosspin 35 and the base is positioned by an adjusting screw 36l and controlknob 37.

A special feature of the control screw is that it has a shoulderedterminal point 38 seated in and projecting from the lower end of thescrew, backed up by a spring 39 and abutment screw 46, providing adesirable amount of yield in the holding action of the adjustment screw.

Service wires 41 and 42 are connected with the iixed end of the switchblade and with the stationary switch contact 26.

The terminals of these wires are of special construction, being showneach as a sleeve 43, FIG. 7, crimped over the bared end of the wire,having an abutment flange 44 at the back and headed over as a tubularrivet at the front end at 45.

This avoids the use of screws and assures the irm securing of the wireto the terminal and the securing y of the terminal to the switchmechanism.

3 movement of the V-strut, as indicated in exaggerated form in FIG. 8.

The interelation of these mechanical movements adds up to a greater andfaster movement of the combined parts, giving a quicker and morepositive responsive action.

With slight movement of the pressure point 32 on the spring switch bladepast the dead center 29 of the spring toggle, the switch blade will snapover from the FIG. 1 to the FIG. 2 position and will remain in thatposition so long as the pressure center 32 remains there but as thepressure point 32 is relieved from the FIG. 2 to the FIG. 1 position,travelling to opposite side of the dead center, the switch blade Will besnapped back to the closed circuit position, FIG. 1.

The V-strut may be made of high expansion material, so as to add to thefast expansive movement of the unit.

The quick responsive action of the unit renders it suitable for manypurposes, particularly Where slight variations in temperature :andcorresponding control are important.

What is claimed is:

1. Snap action thermostat with amplied actuating movement, comprising aheat transfer plate,

=a at bimetal strip having substantially its entire length contiguouswith said heat transfer plate, said bimetal being mounted at asubstantially center point in fixed engagement on said plate, withopposite ends of the same free to curl up away from the plate underthermostatic action,

said free opposite ends of said bimetal strip being bent up intoangularly extended abutment lugs,

said abutment lugs having openings therein,

a spring tensioned switch member, and

an expansible and contractable thrust transmitting strut interposedbetween said bimetal and switch member,

said strut being of inverted V-shaped formation having divergentlyinclined legs yieldingly connected at the center and provided at therdivergent ends of the same with lugs extending through saidperforations in the abutment lugs of the bimetal strip,

whereby t0 :add thrust generated by the closing movement of said legs.to the movement generated by the free ends of said bimetal strip.

References Cited UNITED STATES PATENTS 2,382,182 8/1945 Strong 200-138 X2,689,290 9/1954 Mettler 200--138 3,193,649 7/ 1965 Uhlich 200-1383,193,792 7/ 1965 Shea 174-75 X FOREIGN PATENTS 1,070,758 10/ 1959Germany.

BERNARD A. GILHEANY, Primary Examiner.

R. L. COHRS, Assistant Examiner.

